I neglected to put in the bumper when I was rebuilding the front suspension on my wife's 68. The front subframe was out of the car on jackstands when I realized my mistake. I thought that maybe when I got the car back together the weight would compress the spring and there would be enough space to put it in, but it doesn't sound like it based on your original question. Since I didn't want to wait anyway, I used my spring compressor to take the pressure off the upper control arm, lubed it up and popped it right in.